1. Field of the Invention
The present invention relates to arm assemblies for disk drives. More specifically, the present invention relates to an adapter for coupling an actuator arm with a transducer head.
2. Description of Related Art
Actuator arm assemblies are utilized within disk drive units for positioning a transducer head to read and write data in selected sections of a magnetic storage disk. One or more actuator arms form a part of the actuator arm assembly. Each actuator arm is coupled to a transducer head. The entire arm assembly is pivotable so that each head moves over the surface of its respective disk.
Some disk drive units have multiple magnetic disks in a standard configuration. In these disk drive units, the arm assembly includes a plurality of actuator arms positioned proximate to the stacked disks. Each of the actuator arms is coupled with a transducer head for reading and writing data. Each head contacts its disk with a load pressure provided by a load beam that connects the head with one of the actuator arms. To connect a load beam with an actuator arm, an adapter plate is often used. The load beam is spot welded to the adapter plate, which is fastened to the actuator arm end. A conventional method of fastening the adapter plate to the actuator arm is termed a "ball staking" method.
The ball staking method requires that the adapter plate have a hole formed therein with a sleeve extending therefrom. First, the extended sleeve is inserted in the actuator arm, specifically into a hole formed near the end of the actuator arm. Then, a ball is pressed through the hole in the adapter plate sleeve to deform the sleeve and generate an interference fit between the sleeve and the actuator arm end, thereby affixing the adapter plate to the actuator arm. To generate the required tightness of the interference fit, additional balls having progressively larger diameters may be pushed through. This process can be difficult and time consuming, which can increase manufacturing costs.
The ball staking process is particularly difficult in multiple disk systems, in which at least one actuator arm is positioned between two disks. Each of the two sides of an "in-between" arm has an adapter plate attached to a transducer head, and both of these adapter plates have sleeves that are affixed in the same hole in the actuator arm. If the actuator arm is thick, a reasonably good fit could be provided even if both sleeves have the same diameter. In that instance, both sleeves can be deformed against the hole without overlapping. However, fast, high performance actuator arms are thin to reduce weight, and the two sleeves necessarily overlap. This requires that the inner diameter of a first sleeve fits closely within the outer diameter of a second sleeve. This requires that the inner diameter of a first sleeve fits closely within the outer diameter of a second sleeve. Production of the overlapping configuration is difficult and time consuming, and requires very tight tolerances, particularly between inner and outer diameters of both sleeves and the hole.
In addition to manufacturing difficulties, the ball staking method has other drawbacks. If the adapter plate must be removed from the arm after the ball has been inserted and pressed into place, the only way is by forcible removal which could damage the adapter plate or the actuator arm. This problem is particularly acute when two adapter plates are affixed by overlapping sleeves into the same hole: damage to one or both adapter plates is likely. As a result of this problem, a certain percentage of magnetic head assemblies (defined as the adapter plate, load beam, and head) will be scrapped.
Another problem with the ball staking process is difficulty verifying proper assembly during manufacture. The adapter plate must have a sufficiently tight interference fit. However, it is very difficult to determine if the sides of the extended sleeve are tightly pressed against the hole within the actuator arm and that the plate itself is tightly pressed against the actuator arm end. If adapter plate is not affixed tightly, then undesirable mechanical resonances could be produced, which would result in a substantial reduction in performance.
It would be an advantage to provide an adapter plate coupling for an actuator arm that could easily be coupled to the actuator arm and easily removed therefrom. It would be a further advantage if the adapter plate could be installed on an actuator arm with a predictable pressure during the manufacturing process.